@Luciano Thank you very much for the link, I'd use this to update the KB, but looking deeper I did also notice these traces:

2023-08-18 22:40:40 INFO unit.ceph-mon-nvme/8.juju-log server.go:316 old_version: None
2023-08-18 22:40:40 INFO unit.ceph-mon-nvme/8.juju-log server.go:316 new_version: None
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60 Traceback (most recent call last):
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/config-changed", line 1351, in <module>
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     hooks.execute(sys.argv)
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/charmhelpers/core/hookenv.py", line 962, in execute
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     self._hooks[hook_name]()
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/charmhelpers/contrib/hardening/harden.py", line 93, in _harden_inner2
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     return f(*args, **kwargs)
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/config-changed", line 248, in config_changed
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     check_for_upgrade()
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/config-changed", line 144, in check_for_upgrade
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     old_version_os < new_version_os):
2023-08-18 22:40:41 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60 TypeError: '<' not supported between instances of 'str' and 'NoneType'
2023-08-18 22:40:41 ERROR juju.worker.uniter.operation runhook.go:140 hook "config-changed" (via explicit, bespoke hook script) failed: exit status 1
2023-08-18 22:40:41 INFO juju.worker.uniter resolver.go:145 awaiting error resolution for "config-changed" hook
2023-08-18 22:40:46 INFO juju.worker.uniter resolver.go:145 awaiting error resolution for "config-changed" hook
2023-08-18 22:40:46 INFO unit.ceph-mon-nvme/8.juju-log server.go:316 old_version: None
2023-08-18 22:40:46 INFO unit.ceph-mon-nvme/8.juju-log server.go:316 new_version: None
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60 Traceback (most recent call last):
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/config-changed", line 1351, in <module>
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     hooks.execute(sys.argv)
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/charmhelpers/core/hookenv.py", line 962, in execute
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     self._hooks[hook_name]()
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/charmhelpers/contrib/hardening/harden.py", line 93, in _harden_inner2
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     return f(*args, **kwargs)
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/config-changed", line 248, in config_changed
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     check_for_upgrade()
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60   File "/var/lib/juju/agents/unit-ceph-mon-nvme-8/charm/hooks/config-changed", line 144, in check_for_upgrade
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60     old_version_os < new_version_os):
2023-08-18 22:40:46 WARNING unit.ceph-mon-nvme/8.config-changed logger.go:60 TypeError: '<' not supported between instances of 'str' and 'NoneType'
2023-08-18 22:40:46 ERROR juju.worker.uniter.operation runhook.go:140 hook "config-changed" (via explicit, bespoke hook script) failed: exit status 1
2023-08-18 22:40:46 INFO juju.worker.uniter resolver.go:145 awaiting error resolution for "config-changed" hook
2023-08-18 22:40:57 INFO juju.worker.uniter resolver.go:145 awaiting error resolution for "config-changed" hook
2023-08-18 22:40:57 INFO unit.ceph-mon-nvme/8.juju-log server.go:316 old_version: None
2023-08-18 22:40:57 INFO unit.ceph-mon-nvme/8.juju-log server.go:316 new_version: None